Two component amine nitrate monopropellants and method of propulsion



United States Patent 3,212,254 TWO COMPONENT AMINE NITRATE MONOPRO- PELLANTS AND METHOD OF PROPULSION Homer M. Fox, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware N0 Drawing. Filed Aug. 14, 1957, Ser. No. 678,243 17 Claims. (Cl. 60--35.4)

This application is a continuation-in-part of my copending application Serial No. 465,957, filed November 1, 1954, and my copending application Serial No. 542,- 515, filed October 24, 1955, said latter application now abandoned.

This invention relates to novel two-component monopropellant compositions suitable for use in rocket motors, ram-jets, pulse-jets and the like. In a further aspect, this invention relates to a method of operating such motors.

Rocket motors are operated by burning a mixture of fuel and oxidant in a combustion chamber and causing the resulting gases to be expelled through a nozzle at high velocity. Liquid propellants are preferred over solid propellants where it is necessary to vary thrust during flight. Liquid propellants are classified as bipropel lants and monopropellants and the latter are either a single compound or mixtures of compounds. Monopropellant systems are advantageous in that they require only one tank, one pump, one nozzle, one fuel line, one set of controls, etc. Furthermore, no mixing or proportioning system is required.

The principal elements of a rocket motor utilizing a liquid fuel comprise a combustion chamber, exhaust nozzle, an injection system, and propellant control valves. The propellent gases are produced in the combustion chamber at pressures governed by the chemical characteristics of the propellant, its rate of consumption, and the cross-sectional area of the nozzle throat. The gases are ejected into the atmosphere through the nozzle with supersonic velocity. The function of the nozzle is to convert the pressure of the propellent gases into kinetic energy. The reaction of the discharge of the propellent gases constitute the thrust developed by the rocket motor.

The following are objects of this invention.

An object of this invention is to provide a novel twocomponent monopropellant combination. A further object of this invention is to provide a method for operating rocket motors. v

Other aspects, objects, and advantages of this invention will be apparent to one skilled in the art upon reading this disclosure.

In accordance with the invention there are provided novel two-component monopropellent compositions, suitable for use according to the method of the invention in rocket motors and the like. Broadly speaking, the invention comprises the use of an amine nitrate and a suitable oxidant as a two-component monopropellant.

Thus according to the invention there is provided a two-component monopropellant comprising a mixture of (1) an oxidant and (2) an amine nitrate selected from the group consisting of piperidine nitrate, pyridine nitrite, Z-methylpyridine nitrate, and amine nitrates characterized by a formula selected from the group consisting of wherein: each R is selected from the group consisting of acyclic, 'alicyclic, and aromatic hydrocarbon radicals con- 3,212,254 Patented Oct. 19, 1965 taining from 1 to 8 carbon atoms, and hydrogen; and R is selected from the group consisting of (a) Alkylene, alkenylene, and alkynylene hydrocarbon radicals containing from 1 to 8 carbon atoms, and

,b) {R -X-]- R radicals wherein each R is an alkylene radical containing from 1 to 4 carbon atoms, and X is selected from the group consisting of oxygen, sulfur, and

and

radicals wherein R is defined as above, y is an integer of from 1 to 3, z is an integer of from i to 3, and n is an integer from 1 to 5;

the total number of carbon atoms in the molecule does not exceed 40, and the total number of amine nitrogen atoms in the molecule does not exceed 10.

Examples of amine nitrates suitable for use in the practice of the invention include, among others, the

following:

methylamine nitrate;

dimethylamine nitrate;

trimethylamine nitrate;

mono-, dior triethylamine nitrate;

propylamine nitrate;

isop'ropylamine nitrate;

tertiary butylamine nitrate;

isobutylamine nitrate;

N,N,N',N'-tetramethylbutane-1,2-diamine dinitrate;

N,N,N,N'-tetraethylpentane-1,3-diarnine dinitrate;

N,N,N,N-tetramethylhexane-3,4-diamine dinitrate;

pyridine nitrate;

Z-methylpyridine nitrate;

piperidine nitrate;

tri-n-octylamine nitrate;

N,N-dimethyl-Z-butenyl-l-amine nitrate;

N-ethyI-Z-butynylamine-nitrate;

N-isopropyl-3,5-dimethylcyclohexylamine nitrate;

4-cyclohexeny1amine nitrate;

N,N-dimethylaniline nitrate;

triphenylamine nitrate;

N,N-di-n-octyl-p-tolylamine nitrate;

a-methylbenzylamine nitrate;

diisopropylamine nitrate;

N,N,N,N'-tetramethylethane-1,Z-diamine dinitrate;

N,N,N,N-tetramethylpropane-1,2-diamine dinitrate;

N,N,N',N'-tetramethylbutane-1,3-diamine dinitrate;

ethane-1,2-diamine dinitrite;

N,N,N,N-tetramethyl-Z-butyne-1,4-di-amine dinitrate;

N,N,N',N-tetraethylethane-1,2-diamine dinitrate;

N,N,N',N-tetramethylbutane-1,4-diamine dinitrate;

N,N,N,N'-tetramethyloctene-4,S-diamine dinitrate;

N-phenyl-N'-n-octylethane-1,2-diamine mononitrate;

N,N,N,N-tetra-n-octyloctane-1,2-diamine dinitrate;

N,N,N,N'-tetracyclohexylhexane-2,5-diamine dinitrate;

N,N-di-p-tolylpropane-1,3-diamine mononitrate;

N-u-methylbenzyl-Z-butene-1,4-diamine mononitrate;

N,N'-dicyclohexenylethane-1,Z-diamine dinitrate;

N,N,N,N'-tetramethyl-2-butene-l,4-diamine dinitrate;

N,N,N',N'-tetraethylpropane-1,3-diamine dinitrate;

N-2,4-dimethylcyclohexyl-N-n-octyl-n-octane-1,8-diamine dinitrate;

1,4-diamino-2-butene dinitrate;

3 N,N,N,N-tetraphenyl-n-3-octene-1,3-diamine dinitrate; N,N'-di(2-ethy1hexy1)2-butene-1,4-diamine mononitrate; N,N,N'tri-n-propenyl-2-butene-1,3 diamine dinitrate; N-cyclohexyl-N'-cyclohexenylpropane-1,3-diamine mononitrate; N,N,N',N'-tetraethyl-4-octyne-1,8-diamine dinitrate; N,N'-dimethylethylene-1,2-diamine dinitrate; N,N'di(2,4-dimethylphenyl) -2-butyne-1,4-diamine mononitrate;

,N,N-dicyclohexyl-2-pentyne-1,S-diamine dinitrate;

'N,N,N,N'-tetraethyl-1,3-diamino-2-propanol dinitrate;

N,N-diphenyl-1,9-diamino--nonanol mononitrate; N,N,N',N'-tri-2-ethylcyclohexyl-1,4-diamino-2-butanol dinitrate; N,N-di- (2,4-dimethylphenyl) -1,3-diamino-2-propanol mononitrate; N,N'-dicyclohexenyl-1,4-diamino-2-butanol d-initrate; N,N,N',N'-tetra-n-propenyl-1,6-diamino-4-hexanol mononitrate; N,N-dimethylethane-1,Z-diamine dinitrate; N,N,N',N,N"-pentamethyldiethylenetriamine trinitrate; N,N',N"-tricyclohexyldiethylenetriamine dinitrate; N,N,N,N,N"-pentaphenyldibutylenetriamine trinitratc; N,N-di-p-tolyldipropylenetriamine mononitrate; N,N,N'-tri-n-octyldiethylenetri-arnine trinitrate; N,N,N,N',N"-penta-Z-ethylbutyldiethylene triamine dinitrate; N,N,N"-tri-2-ethylcyclohexenyldiethylenetriamine trinitrate; diethylene triamine trinitrate; N,N,N',N,N",N"-hexamethylpropane-1,2,3triamine tri nitrate; N,N,N",N"'-tetra(2-ethylphenyl)butane-l,2,3,4-tetramine dinitrate; N,N-di(2,4dimethylcyclohexyl)pentane-1,3,5-triamine trinitrate; N,N,N',N,N",N"-hexa-2-butenylpropane-1,2,3-triamine mononitrate: propane-1,2,3-triamine trinitrate; N ,N ,N ,N ,N ,N ,N ,N ,N ,N ,-decamethylpentane,

1,2,3,4,5-pentamine pentanitrate, N ,N ,N ,N ,N -pentaethyltetraethylenepentamine trinitrate, N,N,N,Ntetra-n-propyl-2,4,6-trihydroxyheptane-1,7-

diamine dinitrate, N,N,N',N'-tetramethyl-3,6-dioxaoctane-1,8-diamine dinitrate, and 2,4,6-trithiaheptane-1,7-diamine mononitrate, and 1,2,3,4,6,7,8,10,11,12-deca(N-methylamino)dodecane pentanitrate.

The amine nitrates described above are oxygen deficient and consequently the fuel compositions of my invention require an oxidant. Suitable oxidants that can be used in the two-component monopropellant compositions include anhydrous nitric acid, nitric acid (red and white fuming), hydrogen peroxide, and the liquid nitro substituted aliphatic hydrocarbons such as nitro methane, dinitromethane, trinitromethane, tetranitromethane, nitroethane, dinitroethane, trinitroethane, pentanitropropane, and the like.

Nitric acid is the presently preferred oxidant for use in the practice of the invention. Since water tends to retard a stream of a hypergol such as pyrrole.

combustion of the acid with the fuel, the nitric acid is preferably substantially free of water. Thus, the presently most preferred oxidant is anhydrous nitric acid. However, other more dilute nitric acids can be used in the practice of the invention. White fuming nitric acids and red fuming nitric acids of varying concentrations are available commercially, and all are useful in the practice of this invention. White fuming nitric acid usually contains about to 99 weight percent HNO from 0 to 2 weight percent N0 and up to about 10 weight percent water. Red fuming nitric acid usually contains about 70 to 90 weight percent HNO from 2 to 25 weight percent N0 and up to about 10 weight percent water. Of course, mixtures of the above described acids can be employed to give an acid having any intermediate composition, and all are useful in the practice of this invention. Thus, it has been found t-hatnitric acids of all types containing at least about 70 weight percent HNO are useful as an oxidant in the practice of the invention.

The monopropellants used in the present invention will be preferably near stoichiometric mixtures of oxidant and amine nitrate. The ratio of fuel component to oxidant can be in the range of 0.75 to 1.25 times that of the stoichiometric amount. A slightly fuel-rich mixture is usually required to give an optimum rocket motor performance. Amine nitrates can be prepared by several methods. One method is to react an amine With nitric acid. Another method which can be employed is to form a salt of the amine, such as a hydrochloride or an acetate, and then react the amine salt with nitric acid. When amine nitrates are to be prepared by the direct reaction of an amine with nitric acid, and when nitric acid is to be employed as the oxidant in the monopropellants of the invention, said amine nitrates can be prepared in situ by adding the amine to the calculated amount of nitric acid. However, the normally preferred procedure is to admix the amine nitrate, prepared by any suitable method, with nitric acid or another suitable oxidant in the desired ratio at some time prior to use. The length of storage prior to use will depend upon the storage stability of the particular monopropellant composition being employed as will be shown hereinafter.

The amine nitrate-nitric acid two-component monopropellants of the present invention can be conveniently ignited by contacting a stream of the monopropellant with Any material which is hypergolic when mixed with nitric acid can be used. Other materials hypergolic with nitric acid such as N,N,N',N'-tetramethyl propane-1,3-diamine; N,N,N',N'- tetramethyl propene-1,3-diamine; furfuryl alcohol; ethylene diarnine; etc., can also be used to ignite the two-component monopropellant. These hypergols are simultaneously injected into the combustion chamber with the twocomponent monopropellent to ignite the monopropellent. After the two-component monopropellent is ignited, the flow of hypergol is stopped. A temperature-sensitive element, a time mechanisms or other means can be used to terminate the flow of the hypergol. The other two-component monopropellent compositions of the present invention can be ignited by other means such as, for example, by an electric igniter which, of course, can also be used for amine nitrate-nitric acid mixtures. Suitable apparatus is shown in my copending application, Serial No. 465,957, filed November 1, 1955.

EXAMPLE I A number of runs were made in which polyamine com pounds were reacted with nitric acid to form the corresponding amine nitrates. These runs were carried out according to the following procedure.

An amount of the pure polyamine compound was charged to a flask, after which an amount of aqueous nitric acid was charged slowly to said flask by means M 3,2 12,254 5 of a dropping funnel. The temperature of the flask con tents was maintained within the range of from to 10 TABLE II C. by means of an ice bath and by adjusting the rate I Calculated Wtpment of add1t1on of the nitric acld to keep the temperature of fiorn 1 1 01 (Wt; t i ir r une lgitra t e fer the reaction mass below C. During the addition of u P X :,E%? gf gg ggg ggg the nitric acid, the flask contents were stirred vigorously. 5 After the nitric acid had been charged, the flask contents 371 were stirred for several minutes to insure complete reacgig E- tion, after which said flask contents were poured into apj 5: proximately 5 times its volume of chilled acetone (-10 1 3- 3%; to C.). The amine nitrate precipitated out. This 2411 3510 precipitate was recovered by filtration, washed with cold g f; could not be determmed acetone or ether, and dried in a vacuum desiccator at room 33.8 36.9 temperature. The melting point and stability of the amine 23:3 32;; nitrate were then determined. None of the amine nitrates 23g 3g. 5 which were prepared were found to be shock sensitive to 5 2 1% the blow of a hammer. The results of these runs are given 5 2 below in Table I.

TABLE I Mols Percent Mols Yield of MP. of Run Amine Charged Nitric Acid Aqueous Amine Amine Amine N 0. Charged Acid (Wt. Charged Nitrate, Nitrate,

Percent Percent 0. HNO:\)

N N,N-tetramethylethane-l,2-diamine 0. 606 40. 5 0. 275 96.3 220-221 ,N-tetra.methylpropane-1,2-diamiue 0. 606 33. 4 0. 275 92. 3 177179 NZNtetramethylbutane-1,3-diamine 0. 606 40. 5 0.275 95. 0 115-116 N, -tctramei;hylbutane-1,3-diarniue. 1.19 70.0 0.578 97.0 115-116 ,N-tetra.methyl-2-butyne-1,4-diamine 0. 6 41. 0 0. 285 96. 4 145-146 N,N-tetraethyleth2me-1,2-diamine 0. 0 41. 0 0. 285 76. 5 142-143 N, -tetramethylbutane1,4dian1ine t 0.43 70. 0 0. 208 98.7 173-174 N,N-tetramethylbutane-1,2-diamine-.. O. 70. 0 0. 183 94. 3 173-174 Bis(N,N-diruethylaminoethyl)ether." 1 0.51 70.0 0. 25 72.0 88-93 -tetramethyl-1,3-diamin0-2-propanoL 0.51 70.0 0.25 85.2 120-124 ,N'-tetraethyl 1,3-diamix1o-2-propanol... 0. 51 70. 0 0. 25 91. 2 113-114 0.70 70.0 0. 23 80.0 162-163 0. 53 70. 0 0. 173 65.3 104-106 Inethylethylene-1,2-diatr1ine 0.505 60.0 0.5 125 ,N-tetramethyl-2-butene-1,4-diamine o. 44 70. 0 0. 21 88. s 179-180 ,N-tetraethylpropane-1,S-diamine 0. 42 70. 0 0. 2 97. 0 I57. 5-159. 5

1 In this run, the amine was dissolved in an equal volume of acetone. 2 Not recorded.

Since the liquid propellants of the invention will be used EXAMPLE III at high altitudes or, in some instances may be stored in arctic regions, temperatures in the order of 40 F. will frequently be encountered when employing the monopropellant of the present invention. Thus, preferred monopropellants of this invention are those mixtures of amine nitrate and oxidant in which the solubility of the amine nitrate in the oxidant at 40 F. is greater than the percentage of amine nitrate required in the fuel-oxi dant mixture for stoichiometric combustion to N H 0, and CO Some examples of fuel-oxidant mixtures which meet this requirement, and are thus preferred, are mixtures of white fuming nitric acid with: N,N,N',N'-tetramethylpropane-1,2-diamine dinitrate; N,N,N',N'-tetramethylbutane-1,3-diamine diinitrate; N,N,N,N'-tetraethylethane 1,2-diamine dinitrate; N,N,N',N'-tetraethyl- 1,3 diamino-Z-propanol dinitrate; N,N,N,N',N"-pentamethyldiethylenetriamine trinitrate; N,N,N,N',N",N"- hexamethylpropane 1,2,3 triamine trinitrate; N,N'-dimethylethane-1,2-diamine dinitrate; and N,N,N',N'-tetramethylpropane-1,3-diamine dinitrate.

EXAMPLE II The amine nitrates which were prepared as described in Example I were dissolved in white fuming nitric acid (WFNA) and the solubilities in weight percent of these compounds in the solvent were determined at 40 F. The white fuming nitric acid used had a composition of 92 weight percent HNO and 8 weight percent water. In addition, the weight percent of amine nitrate required in a solution of the amine nitrate in White fuming nitric acid for stoichiometric combustion to H O, CO and N was calculated. The solubilities and calculated stoichiometric requirements are tabulated below as Table II.

The compound from Run 3 of Example I, N,N,N,N'- tetramethylbutane-1,3-diamine dinitrate, was dissolved in white fuming nitric acid (identical to that of Example II) in stoichiometric proportion (calculated to N H 0, and CO plus 5 percent excess of the amine nitrate. This solution was charged to a test tube and placed in an optical bomb under a. nitrogen atmosphere. The amine nitrate-WFNA solution was then ignited. by means of a high resistance electrical wire, and the time required for a 2" long section of the tube contents to be burned was recorded. The burning rate in inches per second for the propellant mixture was then calculated. Two runs were carried out in this manner, one at a bomb pressure of 300 p.s.i.g., and the other at a bomb pressure of 600 psig. At 300 p.s.i.g., the burning rate was found to be 0.08" per second :while the burning rate at 600 .s.i.g., was found to be 0.13" per second.

The freezing point of the above WFNA-amine nitrate mixture was found to be 52 C., While the refractive index at 255 C. was found to be 1.443. The measured density of this mixture was 1.447 (at 26.5 C.).

EXAMPLE IV Performance characteristics of a two-component monopropellent comprising a stoichiometric mixture of methyl amine nitrate with nitric acid and dinitromethane are presented in Table I.

TABLE I Fuel Exhaust 0* I See. sp.

Temp., K Ft./scc. 300 p.s.i.

which was cooled with ice water.

EXAMPLE V Preparation of anhydrous nitric acid To a 5-liter, 3-necked, round bottom flask there were charged 1.5 liters of WFNA (commercial grade-92% nitric acid, 8% water, and containing a trace of N0 Fifteen grams of urea were added to the flask and dry air was bubbled through the mixture at 60 C. for 3 hours or until the presence of nitrogen dioxide as indicated by red coloring was removed. The mixture was cooled to room temperature and 550 milliliters of concentrated sulfuric acid was added. The 3-necked flask was then fitted with a thermometer and a jacketed distillation column Heat was gradually applied as dry air was bubbled through the mixture. A

'51% yield of essentially anhydrous nitric acid which distilled at 50 C. was obtained. It was found that anhydrous nitric acid could be stored at 17.7 C. (0 F.) or frozen solid at Dry Ice temperatures for at least days without the formation of the red nitrogen dioxide coloration which would indicate some decomposition.

As disclosed and claimed in copending application Serial No. 678,244, filed by R. C. Doss on Aug. 14, 1957, it has been found that certain materials when added to nitric acid stabilize said acid against the evolution of various nitrogen oxides. Said stabilizing materials include urea and acetarnine and ammonium fluoride. Table III given below shows burning rates and other properties of a number of the monopropellants of the present invention in some of which a stabilizing additive has been incorporated. A comparison of the results shows that while said additives render the monopropellant more stable with respect to temperature, they have no appreciable effect on said burning rates.

TABLE III N,N,N',N'- N,N,N',N-tetramethy1- N,N,N,N- N,N N, -tetramethyitetramethylpropane-1,3-diamine tetramethylbu ane-1,4,-diamine ethane-1,2-diadinitrate+ propane-1,2- dinitrate mine dinitrate+ diamine dinitrate 1.4% 1.4% 0.79% 1.4% 1.4% 0.79% Acetamide Acetamide NHiF Acetamide Acetamide HNiF Properties of Unmixed Amine Nitrates:

Impact Sensitivity, inch pounds 120 120 120 Wt. percent Solubility in Anh. HNOQ:

75 F 47. 4 32 F 44. 5 46.6 57. 6 38. 5 -40 F 32. 4 42. 3 53. 8 31. 7 ,Properties of Stoichiometric Mixtures of Amine Nitrates and Anhydrous Nitric Acid Plus Indicated Amounts of Stabilizing Agent:

Wt. percent Salt Content of Mixture 39. 1 .1 33.8 Oxidizer to Fuel Ratio, WA/WS 1. 556 1 766 1.960 Freezing Point, F ---7. 6 94 $+4. 8 Mixture Density, g./ml. at 20/4 1. 440 1. 432 1. 411 Storage Stability at 140 F., hrs 2 38 0.040 Burning Rate, inches/see. at

200 p 1 0.102 040 300 n s i 0. 043 0.137 0. 039 0. 045 400 p s i 0.065 0.175 0.077 0. 172 600 p s i 0. 0. 263 0. 256 0. 213 Calculated Performance Values of Mixtures of Amine Nitrates and Anhydrous Nitric Acid:

Maximum Specific Impulse, lb.-sec./lb 223. 5 222. 0 222. 4 223. 0 Optimum Mixture Ratio, WA/W S... 1. 12 1. 30 1. 30 1.

' (5) 6) N,N,N,N-tetramethy1-hutane-1,3-diamine dinitrate N,N,N,N-tetramethylbutane-1,2diamine dini- No. Add. 1.4% Acetamide 0.79% NH4F 1.4% Acetamide trate 1.4% Acetamide 0.79% NHiF Properties of Unmixed Amine Nitrates:

Impact Sensitivity, inch pounds 120 120 Wt. Percent Solubility in Anh. HNO

75 F- 48. 7 32 F 79.8 41. 6 40 F- 61. 2 32. 7 Properties of Stoichiometric Mixtures of Amine Nitrates and Anhydrous Nitric Acid Plus Tndicated Amounts of Stabilizing Agent:

Wt. Percent Salt Content of Mixture 33, g oxidizer to Fuel Ratio, WA/WS & 1 950 Freezing Point, F +19. 4 Mixture Density, g./ml. at 20/4 1 404 Storage Stabilit; at F. hrs 51. 192 164 317 BurningRate, mches/sec. at

200 p s i r 0.070 0.063 0.068 300 13 s i 0. 102 0. 172 0. 183 v400 p s 1 0. 241 0. 208 0. 228 0.067 600 p i 0. 312 0. 303 0. 322 0. Calculated Performance Values of Mixtures of Amine Nitrates and Anhydrous Nitric Acid:

Maximum Specific Impulse, lb.-sec./lb 223. 2 222, 22 Optimumlvlixture Ratio, WA/WS 1. 44 1 44 TABLE IIIContinued N,N,N, -tetramethyl-2- N ,N,N ,N'-tetramethyl-2 N,N,N,.N'-tetramethyl butene-1,4-diamine dinitrate butyne-1,4-diamine dlm'trate ethane-LZdiamine dinitrate +14% Acetamide +1. 1% Acetamide +14% Acetamlde Properties of Unmixed Amine Nitrates:

Impact Sensitivity, inch pounds 120 92 120 Wt. percent Solubility in Anh. HNO

75 F 47. 6 66. 8 32 F 40. 56. 3 59. 9 40 F. 31. 7 38. 8 47. 4 Properties of Stoichiometric Mixtures of Amine Nitrates and Anhydrous Nitric Acid Plus Indicated Amounts of Stabilizing Agent:

Wt. percent Salt Content or Mixture 34. 7 35. 7 5 Oxidizer to Fuel Ratio, WA/SW 1.881 1. 800 2. 280 Freezing Point, F +17. 6 94 -94 Mixture Density, g./n11. at /4 1. 418 422 1. 4114 Storage Stability at 140 F., hrs 7 Burning Rate, inches/sec. at

200 p.s.i. 0. 061 300 psi. 0.084 400 p.s.i.. 0.120 600 p.s.i... 0.152 at 725 p.s.i. Calculated Performance Values of Mixtures of Amine Nitrates and Anhydrous Nitric Acid: Maximum Specific Impulse, lb.-sec./lb 223. 4 224. 7 222. 5 Optimum Mixture Ratio, WA/WS 1.32 1. 20 2. 69

Bis (dmethyl-amino ethyl)- ether dinitrate+1.4%

dlamino-Z-propanol dinitrate N,N,N,N-tetraethyl-1,3- diamino-2-propane dinitrate Acetamide +14% Acetamide +14% Acetamide Properties of Unmixed Amine Nitrates:

Impact Sensitivity, inch pounds 120 120 120 Wt. Percent Solubility in Anh. HNOa:

F 79. 6 55.8 32 F 77. 3 48.1 63.0 40 F 66. 8 35. 5 44. 3 Properties of Stoichiornetric Mixtures of Amino Nitrates and Anhydrous Nitric Acid Plus Indicated Amounts of Stabilizing Agent:

Wt. Percent Salt Content of Mixture 36. 2 38. 9 0 Oxidizer to Fuel Ratio, WA/WS 1. 761 1. 571 2.225 Freezing Point, F --94 -94 94 Mixture Density, gJml. at 20/4 .411 1 450 1. 414 Storage Stability at 140 F., hrs Burning Rate, inches/sec. at-

200 p.s i 0.015 0. 034 0. 127 300 p s i 0.023 0. 059 0. 152 400 p.s i 0.051 0. 093 0.208 600 p.s i 0.238 0.212 0. 345 Calculated Performance Values of Mixtures of Amine Nitrates and Anhydrous Nitric Acid: f

Maximum Specific Impulse, lb.-sec./lb 220. 8 220. 2 219. 9 Optimum Mixture Ratio, WA/WS 1. 31 1. 16 1. 69

Hexane-1,6-diamine N,N-dimethy1- N,N-dimethyl- N ,N,N,N ',N"-

dinitrate+1.4% ethane-1,2-diamine propane-1,2-diamine hexarnethyl-propane- Acetamide dinitrate+1.4% dinitrate+1.4% |1,2,3-triamine trinitrato Acetamide Acetamide +1. 4% Acetamide Properties of Unrnixed Amine N itratcs:

Impact Sensitivity, inch pounds 120 120 120 Wt. percent Solubility in Anh. HNO

75 F 82.5 56. 1 78. 7 32 F- 74.0 51. 2 70. 5 40 F 52. 7 46. 2 56. 0 Properties of Stoichiometric Mixtures of A trates and Anhydrous Nitric Acid Plus Indicated Amounts of Stabilizing Agent:

Wt. percent Salt Content of Mixture 39. 1 48.6 43.1 39.6 Oxidizer to Fuel Ratio, WA/WS 1. 555 1.056 1. 321 1. 523 Freezing Point, F 94 Mixture Density, g./ml. at 20/4 w 1. 451 1.4798 Storage Stability at F., hrs 2 240 0 Burning Rate, inches/sec. at-

200 p.s.i. 0.060 300 p.s.i 0.146 400 p.s.i- 0.200 600 p.s.i- 0.294 Calculated Performance Values of Mixtures of Amine Nitrates and Anhydrous Nitric Acid: 1

Maximum Specific Impulse, lb.-sec.-/lb 221.0 223. 2 221. 8 Optimum Mixture Ratio, WA/WS 1.14 0.72 1. 12

TABLE III-Continued Piperidine N,N,N,N- N,N-d11sopropyl- Diisopropylamine Nitrate+1.4% Acepentamethyl-dieethane'1,2-diamine nitrate tamide thylene-triamine dmitrate+N add. trinitrate Properties of Unmixed Amine Nitrates:

Impact Sensitivity, inch pounds 120 120 62 Wt. percent Solubility in Anh. HNO

750 1 a 32 F 62. 6 82. 6 40 F 57.2 61.4 Properties of Stoichiometric Mixtures of Amine Nitrates and Anhydrous Nitric Acid Plus Indicated Amounts of Stabilizing Agent:

Wt. percent Salt Content of Mixture 33. 8 27. 7 31.1 39. 6 Oxidizer to Fuel Ratio, WA/WS... 1. 958 2.610 2. 216 1.525 Freezing Point, F 94 94 -94 Mixture Density, g./m l. at 20/4 1. 4164 1. 340 1 .400 1. 4817 Storage Stability at 140 F., hrs est. 1 yr. Burning Rate, inches/sec. at

200 p S i d 0. 074 300 p.s.i -L 0. 076 d 0.055 0. 067 400 p.s.i 0. 101 d 0. 063 0. 098 600 11.5.1 0.189 d 0. 088 Calculated Performance Values of Mixtures of Amine Nitrates and Anhydrous Nitric Acid: 1

Maximum Specific Impulse, lb-.sec./1b 223. 3 222.0 222. Optimum Mixture Ratio, WA/WS 1. 94 1. 78 1.09

Ethylenediamine Diethylene-triamine Pyridine Nitrate Diallylamine Nitrate dimtrate trinitrate Properties of Unmixed Amine Nitrates:

Impact Sensitivity, inch pounds 100 120 120 120 Solubility in Anh. HNOE:

75 F 58. 8 62.7 32 F- Solid -40 F Solid Properties of St Nitrates and. Anhydrous Nitric Acid Plus Indicated Amounts of Stabilizing Agent:

Weight Percent Salt Content of Mixture 71. 3 62. 4 3a 0 Oxidizer to Fuel Ratio, WA/WS 0. 402 0. 603 1. 676 Freezing Point, F +1 67 (glass) -94 Mixture Density, gJml. at /4 530 1. 590 1. 441 Stability Stability at 140 F., hrs Burning Rate, inches/sec. at-

00 p.s.i- 300 p s 400 p s 600 p.s Calculated Performance Values of Mixtures of Amine Nitrates and Anhydrous Nitric Acid: l

Maximum Specific Impulse, lb.-sec./lb e 220. 3 219. 5 215. 2 221. 3 Optimum Mixture Ratio, WA/W S 0. 260 0. 1, 22 1.

e WAIWS=weight of acid/weight of amine salt.

b The freezing point is given as the temperature at which salt crystals began to precipitate.

v Densities were determined with a Westphal balance.

d Determined on 20 wt. percent solution of diisopropylamme nitrate in anhydrous nitric acid.

It is to be realized that the test at is a severe test and the mere fact that some compounds give mixtures which have a low storage stability at 140 F. does not; mean that said compounds are not useful in the practice of the invention because, at lower temperatures, mixtures .choice of the most preferred from said select superior liters of the acid-salt solution in a 30 milliliter stainless group of monopropellants.

As many possible embodiments may be made of this invention without departing from the scope thereof, it is to be understood that all matter herein set forth is to be interpreted as illustrative and not in a limiting sense.

The values for Storage Stability at 140 F. given in the above Table III were determined by storing 20 millisteel bomb immersed in a constant temperature bath. Bomb pressure was then recorded versus time in the storage bath until rupture of a 109 p.s.i. safety disc in the bomb.

Referring to said Table III it will be noted that certain not determine 1 Does not include stabilizer.

of the mixtures listed therein are definitely superior with respect to storage stability, impact sensitivity, burning rate, and solubility in anhydrous nitric acid. Of these properties, storage stability is presently considered to be the most important because the longer the acid-salt solutions can be stored the more useful said mixtures are. Since the monopropellants of the invention may possibly be used or stored under desert conditions, 140 F. was chosen as a reasonable maximum temperature at which to measure storage stability. It will be noted that the following compounds formed mixtures which are definitely superior with respect to storage stability.

TABLE IV Number in dinitrate. dinitrate. dinitrate. dinitrate.

It is to be noted that the compounds of Table IV all wherein: each R is selected from the group consisting of acyclic, alicyclic, and aromatic hydrocarbon radicals containing from 1 to 8 carbon atoms, and hydrogen; and R is selected from the group consisting of (a) alkylene, alkenylene, and alkynylene hydrocarbon radicals containing from 1 to 8 carbon atoms, and (b) {R X} R radicals wherein each R is an alkylene radical containing from 1 to 4 carbon atoms, and X is selected from the group consisting of oxygen,

sulfur, and

OH R1 t I and R1 N' Rl LL-I L I J. H

radicals wherein R is defined as above, y is an integer of from 1 to 3, z is an integer of from 1 to 3, and n is an integer of from 1 to 5; the total number of carbon atoms in the molecule does not exceed 40, and the total number of amino nitrogen atoms in the molecule does not exceed the ratio of said amine nitrate to said oxidant being in the range of 6.75 to 1.25 times that of the stoichiometric amount.

2. The monopropellant of claim 1 wherein said amine nitrate is N,N,N',N-tetramethylbutane-1,3-diamine dinitrate.

3. The monopropellant of claim 1 wherein said amine nitrate is N,N,N',N'-tetramethylbutane-1,4-diamine dinitrate.

4. The monopropellant of claim 1 wherein said amine nitrate is N,N,N,N-tetramethylbutane-1,2-diamine dinitrate.

5. The monopropellant of claim 1 wherein said amine nitrate is N,N-dirnethylethane-1,2-diamine dinitrate.

6. The monopropellant of claim 1 wherein said amine nitrate is diisopropyl amine nitrate.

7. In the method for development of thrust by the combustion of a two-component monopropellant in the combustion chamber of a reaction motor, the steps comprising injecting into said combustion chamber a mixture of (1) an oxidant selected from the group consisting of nitric acid containing at least about 70 weight percent HNO and liquid nitro-substituted lower alkanes and (2) an amine nitrate selected from the group consisting of pyridine nitrate, 2-methylpyridine nitrate, piperidine nitrate and amine nitrates characterized by a formula selected from the group consisting of wherein: each R is selected from the group consisting of acyclic, alicyclic, and aromatic hydrocarbon radicals containing from 1 to 8 carbon atoms, and hydrogen; and R is selected from the group consisting of (a) alkylene, alkenylene, and alkynylene hydrocarbon radicals containing from 1 to 8 carbon atoms, and (b) {R X-} R radicals wherein each R is an alkylene radical containing from 1 to 4 carbon atoms, and each X is selected from the group consisting of oxygen, sulfur, and

OH R1 and radicals wherein R is defined as above, y is an integer of from 1 to 3, z is an integer of from 1 to 3,

and n is an integer of from 1 to 5; the total number of carbon atoms in the molecule does not exceed 40, and the total number of amino nitrogen atoms in the molecule does not exceed 10, the ratio of said amine nitrate to said oxidant being in the range of 0.75 to 1.25 times that of the stoichiometric amount; and igniting said mixture.

8. The method of claim 7 wherein said amine nitrate is N,N,N',N'-tetramethylbutane-1,3-diamine dinitrate.

9. The method of claim 7 wherein said amine nitrate is N,N,N,N'-tetramethylbutane-1,4-diamine dinitrate.

10. The method of claim 7 wherein said amine nitrate is N,N,N,N'-tetramethylbutane-1,2diamine dinitrate.

11. The method of claim 7 wherein said amine nitrate is N,N-dimethyl ethane-1,2-diamine dinitrate.

12. The method of claim 1 wherein said amine nitrate is diisopropyl amine nitrate.

13. In the method for development of thrust by the combustion of a two-component monopropellant in the combustion chamber of a reaction motor, the steps comprising: injecting into said combustion chamber a mixture of (1) an oxidant consisting of nitric acid containing at least about 70 weight percent HNO and (2) an amine nitrate, the ratio of said amine nitrate to said oxidant being in the range of 0.75 to 1.25 times that of the stoichiometric amount; igniting said mixture by contacting said mixture with a compound hypergolic with said oxidant; and discontinuing the flow of said hypergolic compound following ignition of said mixture.

14. In the method for development of thrust by the combustion of a two-component monopropellant in the combustion chamber of a reaction motor the steps comprising: injecting into said combustion chamber a mixture of (1) an oxidant consisting of nitric acid containing at least about 70 weight percent HNO and (2) an amine nitrate selected from the group consisting of pyridine nitrate, 2-methylpyridine nitrate, piperidine nitrate, and

amine nitrates characterized by a formula selected from the group consisting of I lh-III-HN and wherein: each R is selected from the group consisting of acyclic, alicyclic, and aromatic hydrocarbon radicals containing'from 1 to 8 carbon atoms, and hydrogen; and R .is selected from the group consisting of and Rr-I-Rr L l L .11 H

radicals wherein R is defined as above, y is an integer of from 1 to 3, and n is an integer of from 1 to 3, and n is an integer of from 1 to 5; the total number of carbon atoms in the molecule does not exceed 40, and the total number of amino nitrogen atoms in the molecule does not exceed igniting said mixture by contacting said mixture with a compound hypergolic with said oxidant and selected from the group consisting of pyrrole, N,N,N',N'-tetramethylpropane-1,3-

diamine, N,N,N,N'-tetrarnethylpropene-1,3-diamine, furfuryl alcohol, and ethylenediamine; discontinuing the flow of said hypergolic compound following ignition of said mixture the ratio of said amine nitrate to said oxidant 5 being in the range of 0.75 to 1.25 times that of the 'stoichiometric amount; and igniting said mixture.

15. A two-component monopropellant consisting essentially of a mixture of (1) an oxidant selected from the group consisting of nitric acid containing at least about 70 weight percent HNO and liquid nitro substituted lower alkanes, and (2) an amine nitrate, the ratio of said amine nitrate to said oxidant being in the range of 0.75 to 1.25 times that of the stoichiometric amount.

16. In the method for development of thrust by the combustion of a two-component monopropellant in the combustion chamber of a reaction motor, the steps comprising injecting into said combustion chamber a mixture of (1) an oxidant selected from the group consisting of nitric acid containing at least about 70- weight percent HNO and liquid nitro substituted lower alkanes, and (2) an amine nitrate, the ratio of said amine nitrate to said oxidant being in the range of 0.75 to 1.25 times that of the stoichiometric amount; and igniting said mixture.

17. A rocket monopropellant which consists of a mixture consisting of approximately stoichiometric proportions of a lower alkyl amine nitrate and nitric acid containing at least 95% HNO by weight.

References Cited by the Examiner UNITED STATES PATENTS 2,542,193 2/51 Hannum. 2,573,471 10/51 Malina et al -35.4 2,637,161 5/53 Tschinkel 6035.4

OTHER REFERENCES Cottrell et a1.: Journal Chemical Society (1951), pp. 1798-4800.

CARL D. QUARFORTH, Primary Examiner.

ROGER L. CAMPBELL, LEON D. ROSDOL,

Examiners.

Patent No.

October 19, 1965 Homer M. Fox It is he reby certifie ent requiri d that error appears in the above numbered patng correction and that the said Letters Patent should read as corrected below.

Column 14 line 20, for R .X R read +R X}- R line 54, for the claim refe 7 column 15,

(SEAL) Attest:

ERNEST W. SWIDER Attesling Officer EDWARD J. BRENNER Commissioner of Patents 

7. IN THE METHOD FOR DEVELOPMENT OF THURST BY THE COMBUSTION OF A TWO COMPONENT MONOPROPELLANT IN THE COMBUSTION CHAMBER OF A REACTION MOTOR, THE STEPS COMPRISING INJECTING INTO SAID COMBUSTION CHAMBER A MIXTURE OF (1) AN OXIDANT SELECTED FROM THE GROUP CONSISTING OF NITRIC ACID CONTAINING AT LEAST ABOUT 70 WEIGHT PERCENT HNO3, AND LIQUID NITRO-SUBSTITUTED LOWER ALKANES AND (2) AN AMINE NITRATE SELECTED FROM THE GROUP CONSISTING OF PYRIDINE NITRATE, 2-METHYLPYRIDINE NITRATE, PIPERIDINE NITRATE AND AMINE NITRATES CHARACTERIZED BY A FORMULA SELECTED FROM THE GROUP CONSISTING OF 